As cats from the Clans settle around the lake, five cats, Brambleclaw, Squirrelflight, Crowfeather, Mistyfoot, and Tawnypelt are chosen to patrol the lake, deciding borders and laying out territories for the four Clans. As they are starting on ShadowClan, Squirrelflight encounters Jacques, in which both the cats get into a battle. Brambleclaw comes to Squirrelflight's aid, but as Brambleclaw joins her, Susan joins Jacques, and they both put up quite a fight for kittypets. Mistyfoot, RiverClan'sdeputy, comes and helps Brambleclaw and Squirrelflight. Crowfeather and Tawnypelt charge across the forest to help the cats, but Jacques' Twoleg screeches something at the doorway. His screeching eventually leading Jacques into running back into his Twoleg nest.
He and Susan brutally attack Talonpaw, a ShadowClan apprentice, when Talonpaw is hunting alone. After managing to drag himself back to camp, the young apprentice dies from his injuries. Rowanclaw, who was his mentor, takes a patrol for revenge, but Susan and Jacques flee for their Twoleg nest, and their Twoleg throws something at the patrol, which wounds Cedarheart. Squirrelflight retells the story to Firestar, adding in that they've been terrorized by him and Susan. Brambleclaw, Brackenfur, Thornclaw, Cloudtail, Rainwhisker, Squirrelflight, Tawnypelt, Russetfur, Rowanclaw, and Oakfur launch an attack on the nest, using Tawnypelt as bait to get Susan and Jacques to come out. When Tawnypelt pretends to cry out for help, Jacques pushes his muzzle into her face, and says that they wouldn't hurt her, but rip a few pawfuls of her fur out.
This is done to cut Susan and Jacques off from the Twoleg nest. Susan and Jacques are let off with a threatening warning: if they ever again harm any Clan cat, they will be killed. He was seen charging at Cloudtail, fighting with Rowanclaw, and fighting with Squirrelflight who pushes him in to Brambleclaw, who pins him to the ground. He is last seen running back to his Twolegs along with Susan.
Jacques does not formally appear, but is mentioned, though not by name, at a Gathering by Blackstar, saying that Toadfoot and Tawnypelt had defeated the two kittypets in a battle at the Twoleg nest. Toadfoot's eye is swollen from a scratch, suggesting the kittypets had put up a decent fight.
Jacques and Susan are mentioned for the first time by their names in this book. They are both described as bullies who attack weaker cats and escape into their Twoleg nest when beginning to lose a fight. It is also mentioned that they were punished for their deeds by ShadowClan and ThunderClan.
Although not mentioned by name, it is mentioned on Russetfur's page that Russetfur played a vital role in establishing the territories by the lake when she took on the troublesome kittypets who lived in a twoleg den amid the pine trees.
Squirrelflight: "Trouble with kittypets? ShadowClan? You're telling me a whole Clan of warriors can't deal with a couple of kittypets?"
Tawnypelt: "It's not funny. Yesterday they caught Talonpaw out on his own. They attacked him and left him wounded. He managed to drag himself back to camp, but he died."
Squirrelflight: "Oh, Tawnypelt, I'm so sorry!"
Tawnypelt: "Rowanclaw, who was Talonpaw's mentor, led a patrol to take revenge. But as soon as the kittypets saw them, they fled back into the nest. Their Twolegs threw hard things at the patrol, and Cedarheart's leg was badly injured. Those kittypets are cowards. They only come after cats who are weak, or alone."
—Tawnypelt to Squirrelflight about Jacques and SusanTwilight, page 179
"ShadowClan warriors fought a battle with the two kittypets at the Twoleg nest. We won't be having anymore trouble with them for a while."